This invention pertains to equipment useful in preparing highway pavement joints for sealing and more particularly to a mobile frame carrying a trolley to hold sand blasting equipment or the like at a proper angle to clean joints in highway pavement.
In the usual paved highway having either a concrete or asphaltic surface, the surface is spaced by joints to allow for expansion and contraction of that surface without cracking. These joints typically run longitudinally of the highway between lanes of travel and transversely at regular spaced intervals. The joints are sealed by a material which will continue to seal the joints as they are closed and opened by the expansion or contraction of the slab between the joints.
To be most effective, the sealing material should cling to the edges of the slab to prevent water from collecting in the joints. Particularly in areas where there may be alternate freezing and thawing, the water can cause problems because of the expansion as the water freezes. Thus, freezing water in the joints can cause cracking and spalling at the joint. Further problems can be caused by non-compressible materials falling into the joint when it is at its widest and then being trapped as the joint narrows; and by traffic impact causing cracking and spalling at the joint surface.
All of the problems noted above are present in new pavement particularly--where the sealing is improper--and more severely in older pavement where the sealing has broken down. Thus, it is important that the sealing be adequately done in the first instance and that periodic maintenance of the seal be properly accomplished.
Both initially and during maintenance, the desired conditions are that the edges of the joints be clear so that the sealing material will bond to those edges creating a true seal. Ordinarily, the edges are cleaned by sand blasting.
Currently, most of the sand blasting is done manually by one or more operators carrying sand blasting nozzles connected to a source of compressed air and sand, and directing the nozzle toward the edge of the slab. Because of human error, the possibilities of which may be enhanced by fatigue, the direction of the nozzle and the speed of advance of the nozzle is rarely either uniform or adequate. Accurate angles of direction of the nozzles are usually specified by highway authorities and those angles are difficult to judge accurately by operators. Dust from the operation may also cause serious health problems for operators who must necessarily stand very close to the nozzle as the sand is emitted.
The present invention obviates many of the problems. By holding the nozzles mechanically at a fixed adjusted angle, the specification of that angle can be readily met. By using a remote control for the movement of the nozzles the operator can be somewhat isolated from the source of dust resulting in a lessened health hazard. By using a mechanical device, a more smooth and regular movement of the nozzles along the joint is assured thus making certain that no area is missed, and that less of the sand blasting is misdirected at areas other than the edge of the slab.